Disc changer device

ABSTRACT

In a disc changer provided with a driving force transmission mechanism using a crank arm, the size of the crank arm is reduced as much as possible and the smooth movement of the tray is realized. The crank arm ( 7 ) is rotated by a driving force of a drive motor ( 5 ). The crank arm ( 7 ) has a distal end ( 71   a ) connected to a guide groove ( 100 ) formed at the tray ( 1 ). When the crank arm ( 7 ) rotates, the distal end ( 71   a ) moves along the guide groove ( 100 ). When the distal end moves through a left end curve ( 120 ) or a right end curve ( 130 ) at opposite ends of the guide groove ( 100 ), the rotational force of the crank arm ( 7 ) is transmitted to the tray ( 1 ), whereby the tray ( 1 ) performs open/close movement. The guide groove ( 100 ) has a bow shape made up of an arcuate intermediate curve ( 110 ), and the left end curve ( 120 ) and the right end curve ( 130 ) which are curved opposite to the intermediate curve ( 110 ), so that the force to be transmitted to the tray ( 1 ) changes continuously. Therefore, the smooth movement of the tray ( 1 ) and the size reduction of the crank arm ( 7 ) are possible.

TECHNICAL FIELD

The present invention relates to a disc changer which is capable ofsuccessively playing a plurality of discs.

BACKGROUND ART

A disc changer is known which is capable of carrying a plurality ofdiscs such as CDs or DVDs mounted thereto and playing the discssuccessively.

An example of such disc changer includes a roulette table having adisc-like shape and formed, at the periphery, with plurality of mountportions to which a plurality of discs are to be mounted, a tray forrotatably supporting the roulette table and moving the periphery (formedwith the mount portions) of the roulette table into and out of the mainbody of the changer, and a pick-up unit arranged at a predeterminedposition (hereinafter referred to as a “reading position”) on a pathalong which the periphery of the roulette table rotates. With the trayaccommodated in the main body, the roulette table is rotated, and thepick-up unit clamps the disc transported to the predetermined readingposition to read the data recorded on the disc.

Further, a disc changer is known in which the driving source for thein/out operation of the tray and the clamping/releasing operation of thepick-up unit comprises a single electric motor and a driving forcetransmission mechanism for transmitting the driving force of theelectric motor selectively to the pick-up unit and the tray. Forexample, JP-A 2002-184080 discloses a disc changer which includes adriving force transmission mechanism comprising a rack formed on thetray and extending in the back and forth direction, a pinion for meshingwith the rack, a cylindrical cam having a circumferential surface partof which is formed with a guide groove inclining vertically and anotherpart of which is formed with teeth, and two-stage gear unit consistingof a large-diameter gear for meshing with the pinion and a speedreduction gear and a small-diameter gear partially formed with teeth formeshing with the teeth of the cylindrical cam.

In the disc changer, the driving force of the electric motor istransmitted to the large-diameter gear via the speed reduction gear, andthe rotational force of the large-diameter gear is converted, by thelarge-diameter gear, the pinion and the rack, into the force forstraight movement in the back and forth direction and transmitted to thetray. Further, by the cylindrical cam and the small-diameter gearrotating along with the large-diameter gear, the rotational force of thesmall-diameter gear is converted into the force for straight movement inthe up and down direction and transmitted to the pick-up unit.

FIGS. 29 and 30 show another known driving force transmission mechanismin which a crank arm 700, a guide groove 1100 formed at a lower surfaceof a tray 1000, and a cylindrical cam 800 transmit the driving force ofa single electric motor 500 to the tray 1000 and to pick-up unit (notshown) while switching therebetween.

FIG. 29 shows the state in which the tray 1000 is accommodated in thedisc changer, whereas FIG. 30 shows the state in which an end of thetray 1000 is pulled out of the disc changer.

It is to be noted that the electric motor 500 as the driving source, aspeed reduction mechanism 600 for transmitting the driving force of theelectric motor 500 to the crank arm 700, the crank arm 700 and thecylindrical cam 800 are arranged below the tray 1000, i.e. on the deeperside with respect to the sheet surface. However, for convenience ofdrawing of the figure, the electric motor 500, the speed reductionmechanism 600, the crank arm 700 and the cylindrical cam 800 are drawnwith solid lines in FIGS. 29 and 30.

Though not illustrated in FIGS. 29 and 30, the pick-up unit in the formof a box is disposed in a recess formed at an upper left portion of thetray 1000. The pick-up unit has a surface facing the cylindrical cam 800and provided with a lever projecting from the surface. The distal end ofthe lever is fitted in a cam groove (not shown) formed on thecircumferential surface of the cylindrical cam 800 as to be inclined tothe vertical (in the direction perpendicular to the sheet surface).

The driving force of the electric motor 500 is transmitted to the crankarm 700 by the speed reduction mechanism 600. When the crank arm 700rotates by the driving force of the electric motor 500, the distal end710 a of the arm portion 710 moves along the guide groove 1100 formed atthe lower surface of the tray 1000. The guide groove 1100 includes anarcuate, intermediate curve 1110 having a radius of curvature equal tothe radius of gyration of the arm portion 710, and a left and a rightstraight ends 1120 and 1130 extending from opposite ends of theintermediate curve 1110.

When the distal end 710 a of the arm portion 710 moves along theintermediate curve 1110 of the guide groove 1100, the rotational forceof the crank arm 700 is not transmitted to the tray 1000 but transmittedonly to the cylindrical cam 800 during when the cylindrical cam mesheswith the crank arm 700. When the distal end 710 a of the arm portion 710moves along the left straight end 1120 or the right straight end 1130 ofthe guide groove 1100, the crank arm 700 disengages from the cylindricalcam 800. Therefore, the rotational force of the crank arm 700 is nottransmitted to the cylindrical cam 800 but transmitted only to the tray1000.

As noted above, in the disc changer shown in FIGS. 29 and 39, thestructure to utilize the driving force of a single electric motor forboth of the in/out operation of the tray 1000 and the discclamping/releasing operation of the pick-up unit is realized by dividingthe range of rotation of the crank arm to transmit the driving force ofthe electric motor into the range for driving the tray and the range fordriving the pick-up unit. Also in the disc changer disclosed in JP-A2002-184080, the rotation range of the two-stage gear is divided intothe range for driving the tray and the range for driving the pick-upunit, and the mechanism for transmitting the driving force of the singleelectric motor is basically the same as that shown in FIGS. 29 and 30.

In the structure disclosed in JP-A 2002-184080, the driving forcetransmission mechanism for transmitting the driving force of theelectric motor to the tray and the pick-up unit by utilizing thetwo-stage gear is complicated and requires a large number of parts. Ascompared to this, the driving force transmission mechanism using a crankarm shown in FIG. 29 utilizes a simple gear structure and a less numberof parts, and hence, is advantageous as the driving force transmissionmechanism of a disc changer.

However, in the conventional driving force transmission mechanismutilizing a crank arm, the guide groove 1100 comprises an arcuate,intermediate curve 1110 and a left and a right straight ends 1120 and1130 connected to opposite ends of the intermediate curve. Therefore,when the distal end 710 a of the arm portion 710 moves from theintermediate curve 1110 to the left straight end 1120 or the rightstraight end 1130, a large rotational force is suddenly transmitted fromthe crank arm 700 to the tray 1000. On the other hand, when the distalend 710 a of the arm portion 710 moves from the left straight end 1120or the right straight end 1130 to the intermediate curve 1110, therotational force which has transmitted from the crank arm 700 to thetray 1000 suddenly disappears. Therefore, the tray 1000 cannot movesmoothly at the start of the movement and the end of the movement.

Further, when the distal end 710 a of the arm portion 710 is rotatedcounterclockwise from the state shown in FIG. 29 so that the distal end710 a of the arm portion 710 reciprocates through the left straight end1120 of the guide groove 1100 and reaches the boundary between the endand the intermediate curve 1110, the distal end 710 a of the arm portion710 has difficulty in moving to the intermediate curve 1110. Therefore,the crank arm 700 need be stopped at this position. The stop position ofthe crank arm 700 corresponds to the position at which the pull-outamount of the tray 100 becomes maximum. When a crank arm 700 having ashorter arm length is used, the guide groove 1100 of the tray 1000 needbe formed closer to the crank arm 700, so that the maximum pull-outamount of the tray 1000 is reduced. Conversely, in the conventionaldriving force transmission mechanism using a crank arm, to increase themaximum pull-out amount of the tray 1000, the arm length of the crankarm 700 need be increased, which leads to an increase in the size of thecrank arm 700.

Further, in the method in which the driving force of the single electricmotor 500 is transmitted to the crank arm 700 and the object to whichthe driving force is transmitted is switched between the tray 1000 andthe pick-up unit depending on the rotation range of the crank arm 700,the operational states of the disc changer (such as a disc changingstate, a disc clamping state or a disc playing state) are related withthe rotation-l position of the Frank arm 700. Therefore, to control theoperation of the disc changer, the rotational position of the crank arm700 need be detected to utilize the detection signals for the control.

For example, at least four operational states need be detected, i.e.,(1) the state in which the tray is pulled out of the housing(hereinafter referred to as the “open stop position”), (2) the state inwhich the tray is completely accommodated in the housing (hereinafterreferred to as the “close stop position”), (3) the state in which thepick-up unit is clamping a disc (hereinafter referred to as the “clampposition”), and (4) the state in which the pick-up unit is not clampinga disc (“clamp release position”). To detect these, it may be consideredto provide switches at the open stop position and the close stopposition of the tray, and the clamp position and the clamp releaseposition of the pick-up unit, for example. In this method, however, alarge number of switches need be provided at widely separated positions.

As another method for detecting the rotational position of the crankarm, it may be considered to attach, to the crank arm, a rotary encodergenerally known as a device for detecting the rotational position of arotating object.

However, in the driving force transmission mechanism of theabove-described disc changer, the rotation range of the crank arm 700 isabout ±150° taking the state shown in FIG. 29 as the referencedirection, and it is only necessary to divide the rotation range intoseveral regions and determine at which one of the regions the crank arm700 locates. However, a rotary encoder can detect angles with accuracywhich is unnecessary high for the above purpose, and accordingly isexpensive. Therefore, to reduce the cost as much as possible, the use ofa rotary encoder is not desirable.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a disc changer whichincludes a driving force transmission mechanism for transmitting thedriving force of a single driving source to a tray and to a pick-up unitwhile switching therebetween and which is capable of reducing the sizeof the crank arm as much as possible, enabling smooth movement of thetray, and detecting the rotational position of the crank arm by a simplestructure.

According to a first aspect of the present invention, there is provideddisc changer comprising: a tray for carrying a plurality of discsmounted thereto, the tray being arranged in a housing movably back andforth into and out of the housing; a driving source for generating adriving force for performing the in-out movement of the tray; and adriving force transmission for transmitting the driving force generatedat the driving source to the tray, the transmission comprising a guidegroove formed at a lower surface of the tray to extend right and leftand a crank arm arranged below the tray in the housing, the crank armincluding a disc-like rotation portion which is rotatable by the drivingforce of the driving source and an arm portion projecting radiallyoutward from an outer circumference of the rotation portion and having adistal end slidably engaging the guide groove. The guide groove has abow shape comprising an arcuate intermediate curve generally conformingto an arcuate path along which distal end of the arm portion moves dueto the rotation of the crank arm, and left and right end curvesextending from opposite ends of the intermediate curve and curvedopposite to the intermediate curve.

According to a second aspect of the present invention, there is provideda disc changer comprising: a tray for carrying a plurality of discsmounted thereto, the tray being arranged in a housing movably back andforth into and out of the housing; a reproducer arranged at apredetermined position in the housing to be displaceable up and down forreproducing information recorded on a disc while clamping the disc onthe tray; a driving source for generating a driving force for performingthe in-out movement of the tray and the displacement of the reproducer;and a driving force transmission for transmitting the driving forcegenerated at the driving source to the tray and to the reproducer whileswitching between the tray and the reproducer, the transmissioncomprising a guide groove formed at a lower surface of the tray toextend right and left, a cam for displacing the reproducer up and downto shift the reproducer between a disc clamp position and a clamprelease position, and a crank arm arranged below the tray in thehousing, the crank arm including a disc-like rotation portion which isrotatable by the driving force of the driving source, an arm portionprojecting radially outward from an outer circumference of the rotationportion and having a distal end slidably engaging the guide groove, anda connection portion formed at part of the outer circumference of therotation portion for connection to the cam to transmit a rotationalforce of the rotation portion to the cam when the distal end of the armportion moves through an intermediate portion of the guide groove. Theguide groove has a bow shape comprising an arcuate intermediate curvegenerally conforming to an arcuate path along which the distal end ofthe arm portion moves due to the rotation of the crank arm, and left andright end curves extending from opposite ends of the intermediate curveand curved opposite to the intermediate curve.

Specifically, the rotational force of the crank arm is transmitted tothe tray during when the distal end of the arm portion moves through theleft end curve or the right end curve of the guide groove, whereas therotational force of the crank arm is transmitted to the reproducer viathe cam during when the distal end of the arm portion moves through theintermediate curve of the guide groove.

Preferably, the tray pulled out of the housing can be kept at an openstop position when the distal end of the arm portion of the crank arm ina process of moving from the left end curve or right end curve towardthe intermediate curve of the guide groove reaches a predeterminedposition in the left end curve or the right end curve. Specifically, thepredetermined position Is adjacent the boundary between the right endcurve or the left end curve and the intermediate curve of the guidegroove.

Preferably, the cam is cylindrical and has a circumferential surfacepart of which is formed with a cam groove inclined with respect to avertical direction and another part of which is formed with teeth, andthe connection portion of the crank arm comprises teeth formed at acircumferential surface of the rotation portion at a position whichfaces the teeth of the cylindrical cam to mesh with the teeth duringwhen the distal end of the arm portion moves through the intermediatecurve of the guide groove.

Further, a detector for detecting operational states of the tray and thereproducer may be provided under the rotation portion of the crank arm.The detector may detect the operational states of the tray and thereproducer by detecting the position of the distal end of the armportion of the crank arm in the guide groove.

Preferably, the detector may detect that the distal end of the armportion of the crank arm is positioned in the intermediate curve of theguide groove, in the left end curve of the guide groove, in the rightend curve of the guide groove, at the position in the left end curve ofthe guide groove which corresponds to the open stop position of thetray, and at the position in the right end curve of the guide groovewhich corresponds to the open stop position of the tray.

In a preferred embodiment, the detector may comprise a plurality of ribsrespectively formed on a plurality of concentric tracks on a lowersurface of the rotation portion of the crank arm, a plurality ofswitches provided below the rotation portion of the crank arm atpositions which face the respective tracks, and a determiner fordetermining the position of the distal end of the arm portion of thecrank arm in the guide groove based on information as to switchingoperation of the switches performed by the ribs in accordance with therotation of the rotation portion of the crank arm. Each of the ribs mayhave opposite ends each of which is formed with a downward slope. Thedeterminer may determine the position of the distal end of the armportion of the crank arm in the guide groove based on combination ofON/OFF information of the plurality of switches.

According to a third aspect of the present invention, there is provideda disc changer comprising: a tray for carrying a plurality of discsmounted thereto, the tray being arranged in a housing movably back andforth into and out of the housing; a reproducer arranged at apredetermined position in the housing to be displaceable up and down forreproducing information recorded on a disc while clamping the disc onthe tray; a driving source for generating a driving force for performingthe in-out movement of the tray and the displacement of the reproducer;and a driving force transmission for transmitting the driving forcegenerated at the driving source to the tray and to the reproducer whileswitching between the tray and the reproducer, the transmissioncomprising a guide groove formed at a lower surface of the tray toextend right and left; a cam for displacing the reproducer up and downto shift the reproducer between a disc clamp position and a clamprelease position, and a crank arm arranged below the tray in thehousing, the crank arm including a disc-like rotation portion which isrotatable by the driving force of the driving source, an arm portionprojecting radially outward from an outer circumference of the rotationportion and having a distal end slidably engaging the guide groove, anda connection portion which is formed at part of the outer circumferenceof the rotation portion for connection to the cam to transmit arotational force of the rotation portion to the cam when the distal endof the arm portion moves through an intermediate portion of the guidegroove. A detector for detecting operational states of the tray and thereproducer is provided under the rotation portion of the crank arm.

Preferably, the detector may at least detect a state in which the trayis pulled out from the housing, a state in which the tray isaccommodated in the housing, a state in which the reproducer clamps adisc, and a state in which the reproducer releases a disc.

In a preferred embodiment, the detector may comprise a plurality of ribsrespectively formed on a plurality concentric tracks on a lower surfaceof the rotation portion of the crank arm, a plurality of switchesprovided under the rotation portion of the crank arm at positions whichface the respective tracks, and a determiner for determining theoperational state of the tray and the reproducer based on information asto switching operation of the switches performed by the ribs inaccordance with the rotation of the rotation portion of the crank arm.Each of the ribs may have opposite ends each of which is formed with adownward slope. The determiner may determine the operational state ofthe tray and the reproducer based on combination of ON/OFF informationof the plurality of switches.

According to the disc changer of the present invention, the rotationportion of the crank arm rotates by the driving force generated at thedriving source so that the distal end of the arm portion of the crankarm rotates while drawing a circular path. Since the distal end of thearm portion of the crank arm slidably engages the bow-shaped guidegroove of the tray, the rotational force of the crank arm is transmittedto the tray when the distal end of the arm portion slides along theguide groove.

The transmission of the rotational force of the crank arm to the tray isperformed when the distal end of the arm portion of the crank arm movesthrough opposite ends of the guide groove, i.e., the left end curve orthe right end curve of the groove, and is not performed when the distalend moves through the intermediate curve provided at the center of theguide groove.

The opposite ends of the guide groove for transmitting the rotationalforce of the crank arm to the tray are curved opposite to theintermediate curve. Therefore, when the distal end of the guide groovemoves from the intermediate curve to the left end curve or the right endcurve of the guide groove with the guide groove positioned on the rearside of the rotation portion of the crank arm, the straight movementforth for moving the tray back and forth, which is generated when thedistal end of the arm portion moves through the left end curve or theright end curve, gradually increases. Therefore, the tray starts to moveslowly to the front side (open direction) from the state accommodatedand stopped in the tray.

Thereafter, as the guide groove moves forward relative to the rotationportion of the crank arm due to the forward movement of the tray, thedistal end of the arm moves so as to reciprocate along the left endcurve or the right end curve. During this movement, the straightmovement forth transmitted to the tray gradually increases as the distalend of the arm moves toward the terminal end of the left end curve orthe right end curve and gradually reduces as the distal end of the armmoves from the terminal end of the left end curve or the right end curvetoward the intermediate curve.

Therefore, the tray which has started to move is pulled out from thehousing while gradually increasing the speed of the movement. Then,while gradually reducing the speed of the movement in the intermediateprocess, the tray is pulled out of the housing and stopped at apredetermined open stop position.

Therefore, in the disc changer according to the present invention, themovement of the tray can be performed smoothly.

Further, although the conventional guide groove includes straightportions extending right and left from opposite ends of the intermediatecurve, the guide groove of the present invention includes curvedportions which extend from opposite ends of the intermediate curve so asto include discontinuous boundary between the intermediate curve andeach straight portion in the conventional guide groove. Therefore,according to the present invention, the boundary between theintermediate curve and each of the curves provided at opposite endsthereof can be made closer to the center of the guide groove than theboundary between the intermediate curve and each of the straightportions provided at opposite ends thereof in the conventional guidegroove.

When the open stop position of the tray is set to the position at whichthe distal end of the arm portion is moved to the above-describedboundary in the guide groove with the guide groove positioned on thefront side relative to the rotation portion of the crank arm, the amountof movement of the distal end of arm portion of the crank arm, and hencethe pull-out amount of the tray can be made larger than the structureutilizing the conventional guide groove. Conversely, when the pull-outamount of the tray is equal, the crank arm can be made smaller than theconventional one.

Further, in the disc changer according to the present invention, theobject to which the rotational force of the crank arm is transmitted isswitched between the tray and the reproducer depending on the rotationalposition of the crank arm. Therefore, by detecting the rotationalposition of the crank arm by using the detector provided under therotation portion of the crank arm, it is possible to detect a pluralityof operational states such as the state in which the tray is pulled outfrom the housing, the state in which the tray is accommodated in thehousing, the state in which the reproducer clamps a disc, and the statein which the reproducer releases a disc, for example.

Therefore, the detector for detecting the operational state of the trayand the reproducer can be made compact. The detector comprises aplurality of ribs provided at the lower surface of the rotationalportion of the crank arm, a plurality of switches operated by the ribsin accordance with the rotation of the crank arm, and a determiner fordetermining the operational state of the tray and the reproducer basedon the operation information of the switches. Therefore, the pluralityof operational states of the tray and the reproducer can be detected byusing the possibly smallest number of switches, whereby the structure ofthe detector can be simplified and the manufacturing cost thereof can bereduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view showing the driving mechanism of a tray and apick-up unit of a disc changer according to the present invention.

FIG. 2 is a perspective view showing the positional relationship betweena crank arm and a cylindrical cam provided on the lower surface side ofthe tray, and the pick-up unit.

FIG. 3 is a perspective view showing the state in which the cylindricalcam meshes with the crank arm.

FIG. 4 is a perspective view showing the state in which cylindrical camdoes not mesh with the crank arm.

FIG. 5 is a perspective view showing the structure of the lower surfaceside of the crank arm.

FIG. 6 is a plan view showing the positional relationship between thecrank arm and the guide groove.

FIG. 7 shows a mechanism for transmitting the driving force of a drivemotor to the crank arm.

FIG. 8 is a sectional view taken along lines X-X in FIG. 7.

FIG. 9 is a plan view showing the structure of the pick-up unit.

FIG. 10 is a side view showing the relationship between the pick-up unitand a chucking cover.

FIG. 11 is a plan view for describing a first operational state.

FIG. 12 is a plan view showing the relationship between the crank arm,the guide groove and the cylindrical cam in the first operational state.

FIG. 13 is a sectional view corresponding to FIG. 8, showing the statesof three switches in the first operational state.

FIG. 14 is a plan view for describing a second operational state.

FIG. 15 is a plan view showing the relationship between the crank arm,the guide groove and the cylindrical cam in the second operationalstate.

FIG. 16 is a sectional view corresponding to FIG. 8, showing the statesof three switches in the second operational state.

FIG. 17 is a plan view for describing a third operational state.

FIG. 18 is a plan view showing the relationship between the crank arm,the guide groove and the cylindrical cam in the third operational state.

FIG. 19 is a sectional view corresponding to FIG. 8, showing the statesof three switches in the third operational state.

FIG. 20 is a plan view for describing a fifth operational state.

FIG. 21 is a plan view showing the relationship between the crank arm,the guide groove and the cylindrical cam in the fifth operational state.

FIG. 22 is a sectional view corresponding to FIG. 8, showing the statesof three switches in the fifth operational state.

FIG. 23 is a plan view for describing a sixth operational state.

FIG. 24 is a plan view showing the relationship between the crank arm,the guide groove and the cylindrical cam in the sixth operational state.

FIG. 25 is a sectional view corresponding to FIG. 8, showing the statesof three switches in the sixth operational state.

FIG. 26 is a plan view for describing a seventh operational state.

FIG. 27 is a plan view showing the relationship between the crank arm,the guide groove and the cylindrical cam in the seventh operationalstate.

FIG. 28 is a sectional view corresponding to FIG. 8, showing the statesof three switches in the seventh operational state.

FIG. 29 is a top view showing the driving mechanism for a tray and apick-up unit of a conventional disc changer.

FIG. 30 shows the state in which the tray is pulled out from the housingby rotating the crank arm from the state shown in FIG. 29.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowwith reference to FIGS. 1-10.

FIG. 1 is a top view showing a driving mechanism of a tray and a pick-upunit of a disc changer according to the present invention. Although adrive motor 5, a speed reduction mechanism 6, a crank arm 7 and acylindrical cam 8 are provided on the lower surface side of the tray 1(deeper side with respect to the sheet surface) and cannot be seenactually, these members are visibly illustrated for convenience of thedescription.

FIG. 2 is a perspective view showing the positional relationship betweenthe crank arm 7 and the cylindrical cam 8 provided on the lower surfaceside of the tray 1, and the pick-up unit 3. FIG. 3 is a perspective viewshowing the state in which the cylindrical cam 8 meshes with the crankarm 7, whereas FIG. 4 is a perspective view showing the state in whichcylindrical cam 8 does not mesh with the crank arm 7.

FIG. 5 is a perspective view showing the structure of the lower surfaceside of the crank arm 7 FIG. 6 shows the positional relationship betweenthe crank arm 7 and a guide groove 8. FIG. 7 shows the driving mechanismfor the tray 1 and the pick-up unit 3. FIG. 8 is a sectional view takenalong lines X-X in FIG. 7.

FIG. 9 is a plan view showing the structure of the pick-up unit 3. FIG.10 is a side view showing the relationship between the pick-up unit anda chucking cover.

The disc changer can accommodate up to six discs, such as CDs or DVDs,for successively playing the discs. As a mechanism for mounting andremoving discs and a mechanism for playing a designated one of themounted discs, the disc changer includes, in a non-illustrated housing,the tray 1, a roulette table 2, the pick-up unit 3 (reproducer), thechucking cover 4 (See FIG. 2), the drive motor 5, the speed reductionmechanism 6, the crank arm 7, the cylindrical cam 8 and a control board9 (See FIG. 2) on which e.g. a microcomputer is mounted.

The tray 1 and the roulette table 2 are the structural elements of thedisc mounting/removing mechanism. The pick-up unit 3 and the chuckingcover 4 are the structural elements of the disc playing mechanism. Thedrive motor 5, the speed reduction mechanism 6, the crank arm 7 and thecylindrical cam 8 are the structural elements of a driver (hereinafterreferred to as the “tray driver”) for moving the tray 1 into and out ofthe main body for mounting and removing a disc, and a driver(hereinafter referred to as the “pick-up unit driver”) for causing thepick-up unit to clamp a disc mounted to the unit to play the disc.

The tray driver and the pick-up unit driver are made up of the drivemotor 5 as a driving source, and a driving force transmission mechanismfor transmitting the driving force of the drive motor 5 to the tray 1and to the pick-up unit 3 while switching therebetween. The speedreduction mechanism 6, the crank arm 7, the cylindrical cam 8, the guidegroove 100 formed at the lower surface (reverse surface located behindthe sheet surface of FIG. 1) of the tray 1 and a pin 34 connecting thepick-up unit 3 to the cylindrical cam 8 are the structural elements ofthe driving force transmission mechanism.

In the disc changer of this embodiment, the driving force of the drivemotor 5 is transmitted to the crank arm 7 to rotate the crank arm 7, andthe rotational force of the crank arm 7 is converted into a force forstraight movement and transmitted to the tray 1 to move the tray 1 intoand out of the main body. The conversion of the rotational movement ofthe crank arm 7 into the straight movement is performed by moving thedistal end 71 a of an arm portion 71 of the clamp arm 7 along thebow-shaped guide groove 100 formed at the lower surface of the tray 1.

Further, by transmitting the rotational force of the crank arm 7 to thecylindrical cam 8, the cylindrical cam 8 rotates to cause the pick-upunit 2 to perform the disc clamping and releasing operation. Thetransmission of the rotational force of the crank arm 7 to thecylindrical cam 8 is performed by meshing intermittent teeth 72 formedat a predetermined position on a circumferential surface of a rotationportion 70 of the crank arm 7 with outer circumferential teeth 81 formedat a predetermined position on the circumferential surface of thecylindrical cam 8.

In the crank arm 7, when the direction extending from the center O (SeeFIG. 6) of the rotation portion 70 to the rear side of the main body inparallel with the back and forth direction is determined as thereference direction of the rotation of the arm portion 71, the armportion 71 is rotatable in the angular range of ±θ (θ is slightlysmaller than 180° and about 160° in this embodiment). In the angularrange ±α (about ±18° in FIG. 1) within the above range, the distal end71 a of the arm portion 71 moves along the intermediate curve of theguide groove 100. During this movement, the rotational force of thecrank arm 7 is not transmitted to the tray 1, while the intermittentteeth 72 of the rotation portion 70 mesh with the outer circumferentialteeth 81 of the cylindrical cam 8 so that the rotational force of thecrank arm 7 is transmitted to the rotation cam 8.

On the other hand, in the angular range from +α to +θ and the angularrange from −α to −θ, the distal end 71 a of the arm portion 71 movesalong opposite curved ends of the guide groove 100. During thismovement, although the rotational force of the crank arm 7 istransmitted to the tray 1, the intermittent teeth 72 of the rotationportion 70 do not mesh with the outer circumferential teeth 81 of thecylindrical cam 8 so that the rotational force of the crank arm 7 is nottransmitted to the rotation cam 8.

To be exact, the points close to the angular positions of ±α, thedriving force of the drive motor 5 is transmitted to the cylindrical cam8 and the tray 1. Therefore, these points serve as the switching pointswhere the switching between the transmission of the driving force of thedrive motor 5 to the cylindrical cam 8 and the transmission to the tray1 is performed with partial overlapping.

Therefore, if the switching points where the target of transmission ofthe driving force is switched is not taken into consideration, theperiod in which the arm portion 71 of the crank arm 7 moves in theangular range of ±α is a period for clamping and releasing a disc by thepick-up unit 3, whereas the period in which the arm portion 71 of thecrank arm 7 moves in the angular range from +α to +θ and the angularrange from αα to −θ is a period for moving the tray 1 into and out ofthe main body.

Although detailed description will be given later, when the arm portion71 of the crank arm 7 moves in the angular range from −α to −θ, thepick-up unit 3 keeps clamping a disc. Therefore, this angular rangecorresponds to a period in which, while playing a disc, the crank arm 7is rotated to move the tray 1 out of and into the main body to change adisc which is not being played.

When the arm portion 71 of the crank arm 7 moves in the angular rangefrom +α to +θ, the pick-up unit 3 does not clamp a disc. Therefore, thisangular range corresponds to a period for rotating the crank arm 7 tomove the tray 1 out of and into and the main body to mount or exchange adisc before playing.

When the arm portion 71 of the crank arm 7 moves in the angular rangefrom −α to +θ, the tray 1 is accommodated in the main body. When the armportion 71 of the crank arm 7 rotates in a direction from the angularposition of +α toward the angular position of −α (clockwise in FIG. 1),the front end of the pick up unit 3 is lifted from the lower surfaceside (clamp release position) to the upper surface side (clamp position)of the tray 1 by the rotation of the cylindrical cam 8, whereby clampingof a disc is performed. Conversely, when the arm portion 71 of the crankarm 7 rotates in a direction from the angular position of −α toward theangular position of +α (counterclockwise in FIG. 1), the front end ofthe pick up unit 3 is lowered from the upper surface side (clampposition) to the lower surface side (clamp release position) of the tray1 by the rotation of the cylindrical cam 8, whereby the clamp releaseoperation is performed. Therefore, this angular range corresponds to aperiod for rotating the crank arm 7 to rotate the cylindrical cam 8 toclamp or release a disc by the pick-up unit 3.

The tray 1 serves to move the roulette table 2 into and out of thehousing. The roulette table 2 serves to load six discs into the housingand transport the disc to be played to a predetermined position withinthe housing. (This position is the position where data is read from thedisc and corresponds to the position of the pick-up unit in FIG. 1.Hereinafter, this position is referred to as the “read position”.)

The tray 1 comprises a plate member of a size capable of carrying theroulette table 2 horizontally. To allow the pick-up unit 3 to move fromthe lower surface side to the upper surface side of the tray 1 to clampa disc, the tray is formed with a rectangular opening (cutout) at therear end which covers the pick-up unit 3 when the tray 1 is accommodatedin the housing (at the location slightly offset to the left from thecenter of the rear end of the tray 1 in FIG. 1).

The roulette table 2 comprises a circular plate having an upper surfaceformed with circular recesses which serve as mount portions 20 forcarrying six discs mounted thereto as radially aligned along theperiphery thereof. The roulette table 2 is rotatably supported by thetray 1. The roulette table is rotated by a driving force of an electricmotor (not shown) provided separately from the drive motor 5.

Each of the mount portions 20 of the roulette table 2 is formed with anopening (cutout) 21 so that, when the mount portion is transported tothe read position by the rotation of the roulette table 2, part of thelower surface of the disc including the center hole faces the pick-upunit 3 located below through the opening formed in the tray 1. When thepick-up unit 3 clamps a disc, the pick-up unit moves upward from aposition below the roulette table 2 beyond the upper surface of theroulette table 2. The opening of the tray 1 and the opening 21 of eachmount portion 20 are provided to allow the upward movement of thepick-up unit.

The tray 1 is supported movably by a pair of rails 10, 10 (See FIG. 2)arranged in the housing to extend in the back and forth direction. Whenthe driving force is transmitted by the crank arm 7 to the tray 1, thetray moves horizontally in the back and forth direction (See FIG. 1)along the rails 10, 10. By the movement of the tray 1 in the back andforth direction, the roulette table 2 is put into and taken out of thehousing.

FIG. 1 shows the state in which the tray 1 is completely accommodated inthe housing (closed state). When the tray 1 moves from the closed statehorizontally to the front side, about half of the roulette table 2 ispulled out of the housing (open state). (In FIG. 1, of the disc mountportions 20 of the roulette table 2, at least two mount portions 20aligned on the front side are completely exposed in the open state.)Though not illustrated, the tray 1 is provided, at a lower portionthereof, with a member which engages a stopper provided in the housingwhen the tray comes to the stop position in the closed state(hereinafter referred to as the “close stop position”) and to the stopposition in the open state (hereinafter referred to as the “open stopposition”). The engagement between the engagement member and the stopperprevents the tray 1 from moving back and forth beyond the close stopposition and the open stop position.

The pick-up unit 3 functions to clamp a disc transported to the readposition by taking out the disc so as to float from the lower side ofthe roulette table 2 and read the information recorded on the disc whilerotating the disc in that state at a predetermined number ofrevolutions. The pick-up unit 3 is arranged at a posit-on whichcorresponds to the opening of the tray 1 when the tray 1 is at the closestop position.

As shown in FIG. 9, the pick-up unit 3 is a box-like member having anelongated rectangular configuration in plan view and a relatively lowheight. The pick-up unit 3 includes a chassis 30 incorporating aturntable 31 which supports the lower surface of a disc and is made of amagnetic material, a spindle motor fixed to the center of the lowersurface of the turntable 31 (not shown because it is located under theturntable 31), an optical component 32 for reading information recordedon a disc and a driving mechanism 33 for moving the optical component 32in the radial direction of a disc (indicated by the arrow in FIG. 9). Asshown in FIG. 10, the pick-up unit 3 is pivotally mounted to the housingvia a rotation shaft 36 projecting from opposite side surfaces of thechassis 30 at the rear end. The front end of the pick-up unit 3 ispivotable up and down about the rotation shaft 36.

As shown in FIGS. 9 and 10, the front end of the chassis 30 is providedwith a pin 34 projecting therefrom. The distal end of the pin isconnected to an outer circumferential groove 80 formed at thecircumferential surface of the cylindrical cam 8, which will bedescribed later. The front end of the chassis 30 is further providedwith a spring 35 having a distal end fixed to the bottom of the housingso that a force in the downward direction is exerted to the front end ofthe pick-up unit 3 by the resilient force of the spring. As shown inFIG. 3, the outer circumferential groove 80 formed at thecircumferential surface of the cylindrical cam 8 is inclined withrespect to the vertical. Therefore, when the pin 34 moves along theouter circumferential groove 80 due to the rotation of the cylindricalcam 8, the front end of the pick-up unit 3 moves up and down.

The front end of the pick-up unit 3 is biased downward by the spring 35.Therefore, in accordance with the rotation of the cylindrical cam 8, thepin 34 moves stably without rattling along the outer circumferentialgroove 80 while being pressed against the lower surface of the outercircumferential groove 80.

As indicated by double-dashed lines in FIG. 10, in the waiting state inwhich a disc is not played or in moving the tray 1 to exchange discs,the front end of the pick-up unit 3 is kept inclined downward about therotation shaft 36 (clamp release state) for avoiding the interferencewith the tray 1. As indicated by solid lines in FIG. 10, in playing adisc, the pick-up unit 3 is kept generally horizontal (clamp state) tosandwich the disc between the turntable 31 and a rotating member 40.

The rotating member 40, which is magnetized and has a disc-like shape,is rotatably supported by the chucking cover 4. The chucking cover 4 isdisposed above the pick-up unit 3. When the front end of the pick-upunit 3 moves upward from under the roulette table 2 and picks up a disc,the rotating member 40 functions to sandwich the disc between itself andthe turntable 31 by utilizing the attraction power of the magneticforce. As shown in FIG. 10, the rotating member 40 is provided at thefront end of the chucking cover 4 and at a position which faces theturntable 31 when the front end of the pick-up unit 3 is lifted.

When the front end of the pick-up unit 3 is lifted to play a disc, theturntable 31 picks up the disc disposed on the roulette table 2 byfloating the disc from the lower side. When the turntable 31 comes closeto the rotating member 40, the rotating member 40 attracts the turntable31 by the magnetic force so that the disc is sandwiched between therotating member 40 and the turntable 31 by the attraction force (clampoperation). When the spindle motor is driven in this state, theturntable 31 rotates, whereby the disc clamped by the turntable 31 andthe rotating member 40 rotates.

The drive motor 5 is a driving source for moving the tray 1 into and outof the housing and for moving the pick-up unit 3 up and down forclamping the disc to be played. The speed reduction mechanism 6 is amechanism for transmitting the driving force of the drive motor 5 to thecrank arm 7. The crank arm 7 functions to transmit the driving force ofthe drive motor 5 transmitted through the speed reduction mechanism 6 tothe tray 1 or the cylindrical cam 8.

As shown in FIG. 7, the speed reduction mechanism 6 comprises two gears60 and 61 provided between the drive motor 5 and the crank arm 7, and abelt 62 looped around the gear 60 and the rotation shaft of the drivemotor 5. The gear 60 is structured as a two-stage gear made up of apulley and a small toothed wheel, whereas the gear 61 is structured as atwo-stage gear made up of a large toothed wheel and a small toothedwheel. The belt 62 is looped around the pulley of the gear 60, and thesmall toothed wheel of the gear 60 and the large toothed wheel of thegear 61 constantly mesh with each other. The small toothed wheel of thegear 61 constantly meshes with constant engagement teeth of the crankarm 7 (which will be described later).

With the above structure, the driving force of the drive motor 5 istransmitted to the gear 60 via the belt 62 and further transmitted tothe crank arm 7 via the gear 61 and the constant engagement teeth 73.The gears 60 and 61 function to adjust and reduce the number ofrevolutions of the drive motor 5 to be transmitted to the crank arm 7and also functions to make the rotational direction of the crank armcorrespond to the rotational direction of the drive motor 5.Specifically, in FIG. 7, when the drive motor 5 rotates clockwise, thecrank arm 7 also rotates clockwise.

The drive motor 5 is controlled by the microcomputer (not shown) mountedon the control board 9. By controlling the driving of the drive motor 5,the microcomputer controls the entire operation of the device such asmoving the tray 1 out of and into the housing, and clamping and playinga disc by the pick-up unit 3. The microcomputer detects the state of thetray 1 (such as the open state, close state, moving state from open toclose or moving state from close to open), or specifically, detectsseven positions of the tray 1 which will be described later and controlsthe driving of the tray 1 and the pick-up unit 3 based on the detectionresults. To input the positional information for detecting the sevenpositions of the tray 1 into the microcomputer, the control board 9 isprovided with three microswitches 94-96 (See FIGS. 7 and 8), whereas thelower surface of the rotation portion 70 of the crank arm 7 is formedwith four ribs 74-76 (See FIG. 7) for turning on and off themicroswitches 94-96. Details of the detection of the position of thetray 1 will be described later.

The crank arm 7 is provided on the lower surface side of the tray 1 soas to rotate within a horizontal plane. The crank arm 7 is so positionedthat the rotation center (the rotation center O of the rotation portion70) corresponds to the rotation center of the roulette table 2 mountedto the tray 1 when the tray 1 is accommodated in the housing. The crankarm 7 is made up of the rotation portion 70 having a disc-like shape,the arm portion 71, the intermittent teeth 72, the constant engagementteeth 73, and the first through the third ribs 74-76 for the rotationalposition detection. The rotation portion 70 functions to receive thedriving force of the drive motor 5 transmitted via the speed reductionmechanism 6 to rotate the crank arm 7. Further, when the crank arm 7rotates in the angular range from −α to +α described above, the rotationportion functions to transmit the driving force to the cylindrical cam 8to pivot the cylindrical cam 8. The arm portion 71 functions to transmitthe rotational force of the crank arm 7 to the tray 1 to move the tray 1straight in the back and forth direction.

The rotation portion 70 and the arm portion 71 are integral with eachother, and the crank arm 7 rotates about the center O of the rotationportion 70 as the rotation axis. When the rotation portion 70 rotates,the distal end 71 a of the arm portion 7 moves to draw a circular path.

As shown in FIG. 3, the distal end 71 a of the arm portion 71 is formedwith a columnar projection projecting in a direction to face the lowersurface of the tray 1. As shown in FIG. 6, the projection of the distalend 71 a of the arm portion 71 is fitted in the bow-shaped guide groove100 formed at the lower surface of the tray 1 to extend right and left(width direction of the device).

The guide groove 100 includes an arcuate, intermediate curve 110 havinga constant radius of curvature R, and a left and a right arcuate endcurves 120 and 130 which are connected to opposite ends of theintermediate curve 110, curved to the intermediate curve 110 and have aradius of curvature r. The radius of curvature R of the intermediatecurve 110 is equal to the distance from the rotation center O of thecrank arm 7 to the distal end 71 a of the arm portion 71. It is to benoted that, since FIG. 6 shows the crank arm 7 and the guide groove 100as viewed from the lower surface side, the orientation of the left endcurve 120 and the right end curve 130 is reversed. That is, the leftside in the figure corresponds to the right side of the tray 1, whereasthe right side in the FIG. corresponds to the left side of the tray 1.

When the distal end 71 a of the arm portion 71 moves while drawing acircular path due to the rotation of the crank arm 7, during when thedistal end 71 a moves through the left end curve 120 or the right endcurve 130 of the guide groove 100, the rotational force is convertedinto a force for straight movement and transmitted to the tray 1 to movethe tray 1 in the back and forth direction. When the distal end 71 a ofthe arm portion 71 moves through the intermediate curve 110 of the guidegroove 100, the rotational force of the crank arm 7 is not transmittedto the tray 1 and the tray 1 is kept stopped, because the intermediatecurve 110 conforms to the circular path of the distal end 71 a of thearm portion 71.

When the crank arm rotates within a predetermined angular range, theintermitted teeth 72 serve to transmit the rotational force of the crankarm 7 to the cylindrical cam 8 by meshing with the outer circumferentialteeth 81 of the cylindrical cam 8, which will be described later. Theintermittent teeth 72 are formed at part of the outermost circumferenceof the rotation portion 70. Specifically, when the direction in whichthe arm portion 71 of the crank arm projects is determined as theangular reference in the rotation direction of the crank arm 7, theintermitted teeth 72 is formed at a position which is opencounterclockwise through about 30° relative to the angular reference(See FIG. 1). The part of the outermost circumference of the rotationportion 70 which is not formed with the intermitted teeth 72 has anarcuate configuration.

The constant engagement teeth 73 are utilized for inputting the drivingforce of the drive motor 5 transmitted through the speed reductionmechanism 6 into the crank arm 7. As shown in FIG. 5, the constantengagement teeth 73 are provided on the lower surface of the rotationportion 70 so as to form a stepped portion with the intermittent teeth72 in the direction of-the rotation axis. The constant engagement teeth73 are smaller in wheel diameter than the intermittent teeth 72. It isto be noted that, in FIG. 5, the lower surface of the rotation portion70 is oriented upward for convenience of illustration.

The constant engagement teeth 73 and the gear 61 of the speed reductionmechanism 6 constantly mesh with each other. The crank arm 7 rotates dueto the transmission of the rotational force from the drive motor 5 tothe constant engagement teeth 73 via the speed reduction mechanism 6.

As noted above, the first through the third ribs 74-76 serve to set theON/Off state of the microswitches 94-96 in accordance with therotational position of the crank arm 7. As shown in FIGS. 5-7, the firstthrough the third ribs 74-76 are formed on the surface of the rotationportion 70 of the crank arm 7 which is opposite to the surface on whichthe arm portion 71 is provided, i.e. the lower surface of the gearmember formed with the constant engagement teeth 73.

The cylindrical cam 8 pivots by a predetermined amount due to thedriving force of the drive motor 5 transmitted via the crank arm 7 tomove up and down the longitudinal front end of the pick-up unit 3 (lowerend in FIG. 1).

The cylindrical cam 8 is positioned between the pick-up unit 3 and thecrank arm 7 to be rotatable within a horizontal plane and includes theouter circumferential groove 80, the outer circumferential teeth 81, andouter circumferential recesses 82 and 83. The outer circumferentialgroove 80 serves to move up and down the front end of the pick-up unit 3by utilizing the rotation of the cylindrical cam 8. As shown in FIGS. 3and 4, the outer circumferential groove 80 is formed at a part of theouter circumferential surface of the cylindrical cam 8 as inclined withrespect to the vertical. The pin 34 of the pick-up unit 3 is received inthe outer circumferential groove 80. When the cylindrical cam 8 rotates,the pin 34 moves along the outer circumferential groove 80, whereby thefront end of the pick-up unit 3 moves up and down. The outercircumferential teeth 81 are formed on the outer circumferential surfaceof the cylindrical cam 8 at a position opposite to the outercircumferential groove 80. The cylindrical cam 8 rotates due to themeshing of the outer circumferential teeth 81 with the intermittentteeth 72 when the arm portion 71 of the crank arm 7 moves near therotation reference position S0.

The outer circumferential recesses 82 and 83 are defined by inwardlycurved surfaces respectively formed continuously to opposite ends of theouter circumferential teeth 81. The curved surfaces of the outercircumferential recesses 82 and 83 generally conform to the curvedsurface of the outermost circumference (which includes the intermittentteeth 72) of the rotation portion 70 of the crank arm 7. The curvedsurfaces of the outer circumferential recesses 82 and 83 are soconfigured that, when the crank arm 7 comes to a position where theintermittent teeth 72 disengage from the outer circumferential teeth 81,the crank arm 7 slips on the cylindrical cam 8. Therefore, thecylindrical cam 8 rotates only when the outer circumferential teeth 81mesh with the intermittent teeth 72 and is kept stationary during otherperiods, whereby the intermittent movement of the cylindrical cam 8 isrealized.

Next, the detection of the position of the tray 1 will be described.

The crank arm 7 is rotatable within the angular rage of about ±160° fromthe rotation reference position S0. By the rotation of the crank arm 7,the tray 1 moves into and out of the housing and the pick-up unit 3moves up and down via the cylindrical cam 8. As noted above, the angularrange of the crank arm 7 in which the tray 1 moves in and out differsfrom the angular range of the crank arm 7 in which the pick-up unit 3moves up and down. Thus, the rotational position of the crank arm 7(specifically, the rotational position of the arm portion 71 from therotation reference position S0) is related with the state of the tray 1and the pick-up unit 3. In this embodiment, therefore, by detecting therotational position of the crank arm 7 by utilizing the threemicroswitches 94-96 and the first through the three ribs 74-76, theseven states determined by the relationship between the state of thetray 1 and the state of the pick-up unit 3 are detected.

Specifically, there are four states of the tray 1, which are (1) thestate in which the tray is stopped at the open stop position, (2) thestate in which the tray is stopped at the close stop position, (3) thestate in which the tray 1 is moving between the open stop position andthe close stop position while the pick-up unit 3 is not clamping a disc,and (4) the state in which the tray 1 is moving between the open stopposition and the close stop position while the pick-up unit 3 isclamping a disc. On the other hand, there are three states of thepick-up unit 3, which are (5) the state in which the pick-up unit is notclamping a disc (pick-up unit 3 is lowered), (6) the state in which thepick-up unit is performing the disc clamp operation (the pick-up unit 3is moving upward), and (7) the state in which the pick-up unit isclamping a disc (pick-up unit 3 is lifted).

When the above states are considered in relation to the rotationalposition of the crank arm 7, the state (1) corresponds to the state inwhich the crank arm 7 is stopped at the position +θ or the position −θ,whereas the state (2) corresponds to the state in which the distal end71 a of the arm portion 71 of the crank arm 7 is positioned within theintermediate curve 110 of the guide groove 100. In FIG. 1, provided thatthe angles at which the distal end 71 a of the arm portion 71 ispositioned at opposite ends of the intermediate curve 110 of the guidegroove 100 are defined as ±α (about ±18° in FIG. 1), the state (2)corresponds to the state in which the crank arm 7 is positioned in theangular range between +α and −α. The state (3) corresponds to the statein which the crank arm 7 is positioned in the angular range between +θand +α (the distal end 71 a is moving through the left end curve 120 ofthe guide groove 100). The state (4) corresponds to the state in whichthe crank arm 7 is positioned in the angular range between −α and −θ(the distal end 71 a is moving through the right end curve 130 of theguide groove 100).

The clamping of a disc by the pick-up unit 3 is started when theintermittent teeth 72 of the crank arm 7 starts to mesh with the outercircumferential teeth 81 of the cylindrical cam 8 and finished when theintermittent teeth 72 is disengaged from the outer circumferential teeth81 of the cylindrical cam 8. The intermittent teeth 72 of the crank arm7 starts to mesh with the outer circumferential teeth 81 of thecylindrical cam 8 when the arm portion 71 of the crank arm 7 comes tothe rotational position of +α, whereas the intermittent teeth 72disengages from the outer circumferential teeth 81 of the cylindricalcam 8 when the arm portion 71 of the crank arm 7 comes to the rotationalposition of −α. Therefore, the state (5) corresponds to the state inwhich the crank arm 7 is positioned in the angular range between +θ and+α (similarly to the state (3)), the state (6) corresponds to the statein which the arm portion 71 of the crank arm 7 is positioned in theangular range between +α and −α (similarly to the state (2)), and thestate (7) corresponds to the state in which the arm portion 71 of thecrank arm 7 is positioned in the angular range between −α and −θ(similarly to the state (4)).

Thus, when the state in which the tray 1 is stopped at the open stopposition is expressed as “open stop”, the state in which the tray 1 isstopped at the close stop position as “close stop”, the state in whichtray is moving as “moving”, the state in which the pick-up unit 3 is notclamping a disc as “CL off”, the state in which the pick-up unit 3 isclamping a disc as “CL on”, the state in which the pick-up unit ismoving upward to clamp a disc as “moving up”, the rotational positionsof the crank arm 7 classified into seven based on the relationshipbetween respective states of the tray 1 and the pick-up unit 3 areexpressed as (the tray state, the pick-up unit state)=(open stop, CLoff), (moving, CL off), (close stop, CL off), (close stop, moving up),(close stop, CL on), (moving, CL on) and (open stop, CL on).

The position (open stop, CL off) corresponds to the rotational positionof +θ, the position (moving, CL off) corresponds to the angular rangebetween +θ and +α, the position (close stop, CL off) corresponds to therotational position of +α, the position (close stop, moving up)corresponds to the angular range between +α and −α, the position (closestop, CL on) corresponds to the rotational position of −α, the position(moving, CL on) corresponds to the angular range between −α and −θ, andthe position (open stop, CL on) corresponds to the rotational positionof −θ. Therefore, when the ON state and the OFF state of themicroswitches 94-96 (SW94, SW95, SW96) are expressed as 1 and 0,respectively, the above-described seven positions of the crank arm 7 inthis embodiment are detected by the following OF/OFF states of the threemicroswitches 94-96. It is to be noted that the following combinationsof 0 and 1 as the detection information on the rotational position ofthe crank arm 7 are merely example and not limitative of the invention.

(1) Open stop position of +θ=(0, 0, 0)

(2) Angular range between +θ and +α=(1, 0, 0)

(3) Rotational position of +α=(1, 0, 1)

(4) Angular range between +α and −α=(0, 0, 1)

(5) Rotational position of −α=(0, 1, 1)

(6) Angular range between −α and −θ=(0, 1, 0)

(7) Open stop position of −θ=(1, 1, 0)

Therefore, the first through the third ribs 74-76 are formed intopredetermined lengths at predetermined positions on the lower surface ofthe rotation portion 70 of the crank arm 7 so that the above-describedON/OFF states (1)-(7) of the microswitches 94-96 can be realized inaccordance with the rotation of the crank arm 7.

Specifically, the first rib 74 is formed on the circumference of alargest circle, the second rib 75 is formed on the circumference of amiddle circle, and the third rib 76 is formed on the circumference of asmallest circle. The first rib 74 is formed at two portions of thelargest circumference. Each of the ribs 74-76 has opposite ends formedwith slopes to reduce the shock caused by the contact of the lever ofthe corresponding microswitch 94-96 as a result of the relative movementof the microswitch due to the rotation of the crank arm 7.

As shown in FIG. 7, the crank arm 7 and the control board 9 are mountedto the housing so as to partially overlap each other. The first throughthe third microswitches 94-96 are provided at the portion of the controlboard 9 which overlaps the crank arm 7. Specifically, the first rib 74is formed at a position corresponding to the first microswitch 94. Whenthe crank arm 7 is positioned within the above-described angular rangeof (2), (3) and (7), the first rib 74 comes into contact with the firstmicroswitch 94 to turn on the first microswitch 94. Similarly, thesecond rib 75 is formed at a position corresponding to the secondmicroswitch 95. When the crank arm 7 is positioned within theabove-described angular range of (5), (6) and (7), the second rib 75comes into contact with the second microswitch 95 to turn on the secondmicroswitch 95. The third rib 76 is formed at a position correspondingto the third microswitch 96. When the crank arm 7 is positioned withinthe above-described angular range of (3), (4) and (5), the third rib 76comes into contact with the third microswitch 96 to turn on the thirdmicroswitch 96.

For example, FIGS. 7 and 8 show the state when the crank arm 7 ispositioned within the angular range between +α and −α. In this state,only the third rib 76 comes into contact with the third microswitch 96,so that the ON/OFF states of the first through the third microswitches94-96 become “OFF”, “OFF” and “ON”, respectively.

The detection signals indicating the ON/OFF states of the microswitches94-96 are inputted into the microcomputer on the position of the crankarm 7, i.e., the state of the tray 1 and the pick-up unit 3 can bedetected. Therefore, the microcomputer can always monitor the state ofthe tray 1 and the pick-up unit 3. Therefore, even when the operation ofthe tray 1 or the pick-up unit 3 is stopped by any failure, for example,the tray and the pick-up unit can be reliably returned to the originalstate or the initial state after the failure is recovered.

The operation will be described below.

Hereinafter, description will be given individually as to the sevenoperational states realized by the rotation of the arm portion 71 of thecrank arm 7 to the above-described seven rotational positions.Specifically, the description will be given as to the state at eachposition in the case where the crank arm 7 is rotated clockwise from theopen stop position of +θ to the open stop position of −θ. Since theoperation in the case where the crank arm 7 is rotated counterclockwisefrom the open stop position of −θ to the open stop position of +θ isjust the opposite, the description thereof is omitted.

FIGS. 11-28 are views for describing the operation. FIGS. 11-19 show thestate (disc is not clamped) in which the front end of the pick-up unit 3is positioned at the lowermost position (clamp release position),whereas FIGS. 20-28 show the state (disc is clamped) in which the frontend of the pick-up unit 3 is positioned at the uppermost position (clampposition).

FIGS. 11-13 show the state in which the tray 1 is held at the open stopposition of +θ (first operational state, See the state (1)), FIGS. 14-16show the state in which the tray 1 is moving from the open stop positionto the close stop position with the pick-up unit 3 held at the clamprelease position (second operational state, See the state (2)), andFIGS. 17-19 show the state in which the tray 1 is held at the close stopposition (third operational state, See the state (3)). The operationalstate (fourth operational state, See the state (4)) in which the tray 1is held at the close stop position while the pick-up unit 3 is moving upand down will be described with reference to FIGS. 1, 7 and 8. FIGS.20-22 show the state in which the tray 1 is held at the close stopposition (fifth operational state, See the state (5)). FIGS. 23-25 showthe state in which tray 1 is moving from the close stop position to theopen stop position with the pick-up unit 3 held at the clamp position,(sixth operational state, See the state (6)). FIGS. 26-28 show the statein which the tray 1 is held at the open stop position of −θ (seventhoperational state, See the state (7)).

[First Operational State] (See FIGS. 11-13)

The first operational state is a state in which, with no disc beingplayed, the tray 1 is pulled out from the housing for mounting a disc tobe played to the roulette table 2 or exchanging discs. In the firstoperational state, the user can mount a disc to or remove a disc fromthe mount portion 20 of the roulette table 2 which is pulled out fromthe housing together with the tray 1. By rotating the roulette table 2,the mount portion 20 positioned deep in the housing can be moved to theoutside of the housing, so that all of the six discs can be exchanged.

In the first operational state, the arm portion 71 of the crank arm 7 isin the state rotated counterclockwise through the rotational angle ofabout +θ (about +160° in FIGS. 11 and 12) from the rotation referenceposition S0. When the crank arm 7 rotates counterclockwise from therotation reference position S0, the distal end 71 a of the arm 71 movesfrom the center of the intermediate curve 110 toward the left end curve120 of the guide groove 100 of the tray 1. During when the distal end 71a of the arm portion 71 moves through the intermediate curve 110 of theguide groove 100, the intermittent teeth 72 of the crank arm 7 mesh withthe outer circumferential teeth 81, whereby the cylindrical cam 8rotates clockwise in accordance with the rotation of the crank arm 7 tolower the front end of the pick-up unit 3. In this way, the pick-up unit3 is set to the clamp release position.

When the distal end 71 a of the arm portion 71 moves from theintermediate curve 110 to the left end curve 120 of the guide grove 100,the intermittent teeth 72 of the crank arm 7 disengage from the outercircumferential teeth 81. Thereafter, when the distal end 71 a of thearm portion 71 moves through the left end curve 120, the rotationalforce of the crank arm 7 is transmitted to the tray 1 only, whereby thetray 1 moves from the closed stop position toward the open stopposition. By this movement of the tray 1, the guide groove 100 movestoward the front relative to the crank arm 7. As shown in FIG. 11, whenthe distal end 71 a of the arm portion 71 comes to a first rotationalposition S1 slightly deviated to the left within the intermediate curve110 of the guide groove 100 (the position which forms the rotationalangle of about +θ from the rotation reference position S0), the rotationof the crank arm 7 is stopped. Therefore, when the distal end 71 a ofthe arm portion 71 is positioned at the first rotational position S1,the tray 1 is positioned at the open stop position for exchanging discswith no disc being played.

As shown in FIGS. 12 and 13, in the first operational state, all of thefirst through the third ribs 74-76 are located at positions for avoidingcontact with the first through the third microswitches 94-96. Therefore,all of the first through the third microswitches 94-96 are kept “OFF”.From such a state of the switches, the microcomputer determines that thetray 1 and the pick-up unit 3 are in the first operational state.Specifically, from the states of the first through the thirdmicroswitches 94-96 all of which are “OFF”, it is determined that thetray 1 is at the open stop position for exchanging discs with no discbeing played.

[Second Operational State] (See FIGS. 14-16)

The second operational state is a state in which, with no disc beingplayed, the tray which has once pulled out from the housing is moved tobe accommodated into the housing for accommodation of the discs.Specifically, when a non-illustrated eject switch, for example, isoperated after discs are mounted to the roulette table 2 in the firstoperational state, the crank arm 7 is rotated clockwise through apredetermined angle of (θ-α), whereby the first operational state shiftsto the second operational state. At this time, the distal end 71 a ofthe arm portion 71 moves from the first rotational position S1 in theintermediate curve 110 of the guide groove 100 toward the left end curve120. During when the distal end 71 a of the arm portion 71 moves throughthe left end curve 120, the rotational force of the crank arm 7 istransmitted to the tray 1 only, whereby the tray 1 moves from the openstop position toward the close stop position. In the rotation, thedistal end 71 a of the arm portion 71 passes through a second rotationalposition S2 which forms the rotational angle of +β (about +108° in FIGS.14 and 15) from the rotational reference position S0.

Since the left end curve 120 is gently arcuate, as the distal end 71 aof the arm portion 71 moves to the left end curve 120 and further movestoward the left, the force transmitted from the crank arm 7 to the tray1 as converted into the straight movement force gradually increases.Therefore, the tray 1 starts the closing movement slowly, and the speedof the movement increases gradually. When the distal end 71 a of the armportion 71 turns back at the end of the left end curve 120 and passesthrough the second rotational position S2, the force transmitted fromthe crank arm 7 to the tray 1 gradually decreases as the distal end ofthe arm portion moves toward the intermediate curve 110. In this way,the tray 1 moves to the close stop position while decreasing the speedof the movement.

In the second operational state, the intermittent teeth 72 of the crankarm 7 do not mesh with the outer circumferential teeth 81, so that therotation portion 70 of the crank arm 7 slips on the cylindrical cam 8.Therefore, the pick-up unit 3 is held at the clamp release position.

As shown in FIGS. 15 and 16, in the second operational state, only thefirst rib 74 comes into contact with the first microswitch 94, whereasthe second and the third ribs 75 and 76 are located at positions foravoiding contact with the second and the third microswitches 95 and 96,respectively. Therefore, only the first microswitch 94 is kept “ON”,whereas the second and the third microswitches 95 and 96 are kept “OFF”.From such a state of the switches, the microcomputer determines that thetray 1 and the pick-up unit 3 are in the second operational state.Specifically, from the states of the first through the thirdmicroswitches 94-96 which are “ON”, “OFF” and “OFF”, respectively, it isdetermined that the tray 1 is moving from the open stop position forexchanging discs to be played to the close stop position, with no discbeing played.

[The third Operational State] (See FIGS. 17-19)

The third operational state is a state in which the tray 1 is completelyaccommodated in the housing. In the third operational state, the distalend 71 a of the arm portion 71 is held at a third rotational positionS3, which forms a rotational angle of +α (about +18° in FIGS. 17 and 18)from the rotation reference position S0, and the rotation of the crankarm 7 is stopped.

Immediately before the crank arm 7 stops, the distal end 71 a of the armportion 71 moves through the left end curve 120 of the guide groove 100toward the intermediate curve 110. As noted above, since the left endcurve 120 is gently arcuate, as the distal end 71 a of the arm portion71 moves through the left end curve 120 toward the intermediate curve110, the force transmitted from the crank arm 7 to the tray 1 graduallyreduces, so that the speed of the movement of the tray 1 is reduced.When the distal end 71 a of the arm portion 71 moving from the left endcurve 120 reaches the position slightly inside of the intermediate curve110, the rotation center of the roulette table 2 of the tray 1 and therotation center O of the crank arm 7 substantially correspond to eachother, i.e., the rotation center of the arm portion 71 and the center ofcurvature of the intermediate curve 110 of the guide groove 100substantially correspond to each other. As a result, the rotationalforce of the crank arm 7 is not transmitted to the tray 1, so that thetray 1 stops. Further, a stopper provided on the housing also hindersthe movement of the tray 1 to stop the tray 1.

In the third operational state, the intermittent teeth 72 of the crankarm 7 is located at a position directly before meshing with the outercircumferential teeth 81 of the cylindrical cam 8 and is not meshingwith the outer circumferential teeth 81. Therefore, the pick-up unit 3is held at the clamp release position.

As shown in FIGS. 18 and 19, in the third operational state, the firstand the third ribs 74 and 76 come into contact with the first and thethird microswitches 94 and 96, respectively, whereas the second rib 75is located at a position for avoiding contact with the secondmicroswitch 95. Therefore, the first and the third microswitches 94 and96 are kept “ON”, whereas the second microswitch 95 is kept “OFF”. Fromsuch a state of the switches, the microcomputer determines that the tray1 and the pick-up unit 3 are in the third operational state.Specifically, from the states of the first through the thirdmicroswitches 94-96 which are “ON”, “OFF” and “ON”, respectively, it isdetermined that the tray 1 is stopped at the close stop position aftermoving from the open stop position for exchanging discs to be played,with no disc being played.

[Fourth Operation State] (See FIGS. 1, 7 and 8)

The fourth operational state is a state in which the pick-up unit 3 ismoved up and down for clamping or releasing a disc in the housing. Thefourth operation is not performed successively after the thirdoperational state but performed after the user designates the disc to beplayed and that disc is transported to the predetermined clamp positionby the rotation of the roulette table 2. When a disc is not played, thetray 1 is held at the close stop position, with the distal end 71 a ofthe arm portion 71 located at the third rotational position S3. In thisstate, when the disc to be played is transported to the clamp position,the microcomputer rotates the crank arm 7 clockwise through apredetermined angle (2α) At this time, the distal end 71 a of the crankarm 71 moves from left to right along the intermediate curve 110 of theguide groove 100 and passes through a fourth rotational position S4which is the same position as the rotational reference position so.

During when the distal end 71 a of the arm portion 71 moves through theintermediate curve 110 of the guide groove 100, the intermittent teeth72 of the crank arm 7 mesh with the outer circumferential teeth 81.Therefore, the cylindrical cam 8 rotates counterclockwise in accordancewith the rotation of the crank arm 7, whereby the front end of thepick-up unit 3 moves up. In this way, the pick-up unit 3 is set to theclamp position.

Due to the upward movement of the front end of the pick-up unit 3, theturntable 31 lifts the disc so that the disc is clamped by the turntable31 and the rotating member 40 of the chucking cover 4. During thisoperation, the rotation center of the arm portion 71 corresponds to thecenter of curvature of the intermediate curve 110. Therefore, therotational force of the crank arm 7 is not transmitted to the tray 1, sothat the tray 1 is held at the close stop position.

As shown in FIGS. 7 and 8, in the fourth operational state, only thethird rib 76 comes into contact with the third microswitch 96, whereasthe first and the second ribs 74 and 75 are located at positions foravoiding contact with the first and the second microswitches 94 and 95,respectively. Therefore, the third microswitch 96 is kept “ON”, whereasthe first and the second microswitches 94 and 95 are kept “OFF”. Fromsuch a state of the switches, the microcomputer determines that the tray1 and the pick-up unit 3 are in the fourth operational state.Specifically, from the states of the first through the thirdmicroswitches 94-96 which are “OFF”, “OFF” and “ON”, respectively, it isdetermined that the tray 1 is located at the close stop position in thehousing while the pick-up unit 3 is moving up and down to clamp orrelease a disc.

[Fifth Operational State] (See FIGS. 20-22)

The fifth operational state is a state in which, with the tray 1completely accommodated in the housing, a disc clamped by the pick-upunit 3 is played or waits to be played. In the fourth operational state,when the distal end 71 a of the arm portion 71 moving to the rightthrough the intermediate curve 110 of the guide groove 100 comes to afifth rotational position S5 within the intermediate curve 110 whichforms the rotational angle of −α (about −18° in FIGS. 20 and 21) fromthe rotation reference position S0, the rotation of the crank arm 7 isstopped. During when the distal end 71 a of the arm portion 70 movesthrough the intermediate curve 110 of the guide groove 100, theintermittent teeth 72 of the crank arm 7 mesh with the outercircumferential teeth 81, so that the cylindrical cam 8 rotatescounterclockwise in accordance with the rotation of the crank arm 7.However, when the distal end 71 a of the arm portion 71 comes to thefifth rotational position S5, the intermittent teeth 72 of the crank arm7 disengage from the outer circumferential teeth 81, so that therotation of the cylindrical cam 8 is stopped. As a result, the upwardmovement of the pick-up unit 3 is stopped. In this way, the pick-up unit3 is set to the clamp position.

During when the distal end 71 a of the arm portion 71 moves through theintermediate curve 110 of the guide groove 100, the rotational force ofthe crank arm 7 is not transmitted to the tray 1, so that the tray 1 isheld at the close stop position.

As shown in FIGS. 21 and 22, in the fifth operational state, the secondand the third ribs 75 and 76 come into contact with the second and thethird microswitches 95 and 96, respectively, whereas the first rib 74 islocated at a position for avoiding contact with the first microswitch94. Therefore, the second and the third microswitches 95 and 96 are kept“ON”, whereas the first microswitch 94 is kept “OFF”. From such a stateof the switches, the microcomputer determines that the tray 1 and thepick-up unit 3 are in the fifth operational state. Specifically, fromthe states of the first through the third microswitches 94-96 which are“OFF”, “ON” and “ON”, respectively, it is determined that the tray 1 islocated at the close stop position within the housing while the pick-upunit 3 is held at the disc clamp position.

[Sixth Operational State] (See FIGS. 23-25)

The sixth operational state is a state in which, with the disc clampedby the pick-up unit 3 being played or waiting to be played, the tray 1is being pulled out from the housing for exchanging other discs. Thesixth operation is not performed successively after the fifthoperational state but performed upon the user's operation of e.g. aneject switch during the playing of a disc. When the user operates e.g.an eject switch during the playing of a disc, the microcomputer rotatesthe crank arm 7 further clockwise through a predetermined angle (θ-α).Due to this rotation, the distal end 71 a of the crank arm 7 moves fromthe fifth rotational position S5 in the intermediate curve 110 of theguide groove 100 to the right end curve 130. During when the distal end71 a of the arm portion 71 moves through the right end curve 130, therotational force of the crank arm 7 is transmitted to the tray 1 only,so that the tray 1 moves from the close stop position toward the openstop position. During this rotation, the distal end 71 a of the armportion 71 passes through a sixth rotational position S6 which forms arotational angle of −α (about −18° in FIGS. 23 and 24) from the rotationreference position S0.

Similarly to the left end curve 120, the right end curve 130 is alsogently arcuate. Therefore, as the distal end 71 a of the arm portion 71moves to the right end curve 130 and further moves to the right, theforce transmitted from the crank arm 7 to the tray 1 as converted intothe straight movement force gradually increases. Therefore, the tray 1starts the opening movement slowly, and the speed of the movementincreases gradually. When the distal end 71 a of the arm portion 71turns back at the end of the right end curve 130 and passes through thesixth rotational position S6, the force transmitted from the crank arm 7to the tray 1 gradually decreases as the distal end of the arm portionmoves toward the intermediate curve 110. Therefore, the tray 1 moves tothe open stop position while decreasing the speed of the movement.

In the sixth operational state, the intermittent teeth 72 of the crankarm 7 do not mesh with the outer circumferential teeth 81, so that therotation portion 70 of the crank arm 7 slips on the cylindrical cam 8.Therefore, the pick-up unit 3 is held at the clamp position.

As shown in FIGS. 24 and 25, in the sixth operational state, only thesecond rib 75 comes into contact with the second microswitch 95, whereasthe first and the third ribs 74 and 76 are located at positions foravoiding contact with the first and the third microswitches 94 and 96,respectively. Therefore, the second microswitch 95 is kept “ON”, whereasthe first and the third microswitches 94 and 96 are kept “OFF”. Fromsuch a state of the switches, the microcomputer determines that the tray1 and the pick-up unit 3 are in the sixth operational state.Specifically, from the states of the first through the thirdmicroswitches 94-96 which are “OFF”, “ON” and “OFF”, respectively, it isdetermined that the pick-up unit 3 is holding a disc for rotation forplaying while the tray 1 is moving between the close stop position andthe open stop position.

[Seventh Operational State] (See FIGS. 26-28)

The seventh operational state is a state in which, with a disc beingplayed or waiting to be played, the tray 1 is pulled out from thehousing for exchanging other discs. Even during the playing of a discwithin the housing, the user can mount a disc to the mount portion 20 orremove a disc from the mount portion 20 of the roulette table 2 which ispulled out from the housing along with the tray 1.

In the seventh operational state, the arm portion 71 of the crank arm 7is in the state rotated clockwise through the rotational angle of about−θ (about −160° in FIGS. 11 and 12) from the rotation reference positionS0. When the crank arm 7 rotates clockwise, the distal end 71 a of thearm portion 71 moves from the sixth rotational position S6 in the guidegroove 100 of the tray 1 toward the right end curve 130. During when thedistal end 71 a of the arm portion 71 moves through the right end curve130, the rotational force of the crank arm 7 is transmitted to the tray1 only, so that the tray 1 moves from the close stop position toward theopen stop position. By this movement of the tray 1, the guide groove 100moves toward the front relative to the crank arm 7. As shown in FIG. 27,when the distal end 71 a of the arm portion 71 comes to a seventhrotational position S7 slightly deviated to the right within theintermediate curve 110 of the guide groove 100 (the position which formsthe rotational angle of about −θ from the rotation reference positionS0), the rotation of the crank arm 7 is stopped. Therefore, when thedistal end 71 a of the arm portion 71 is located at the seventhrotational position S7, the tray 1 is positioned at the open stopposition for mounting a disc or exchanging discs while playing a disc.

During when the distal end 71 a of the arm portion 71 moves from thesixth rotational position S6 to the seventh rotational position S7, theintermittent teeth 72 of the crank arm 7 do not mesh with the outercircumferential teeth 81, so that the pick-up unit 3 is held at theclamp position.

As shown in FIGS. 27 and 28, in the seventh operational state, the firstand the second ribs 74 and 75 come into contact with the first and thesecond microswitches 94 and 95, respectively, whereas the third rib 76is located at a position for avoiding contact with the third microswitch96. Therefore, the first and the second microswitches 94 and 95 are kept“ON”, whereas the third microswitch 96 is kept “OFF”. From such a stateof the switches, the microcomputer determines that the tray 1 and thepick-up unit 3 are in the seventh operational state. Specifically, fromthe states of the first through the third microswitches 94-96 which are“ON”, “ON” and “OFF”, respectively, it is determined that the tray 1 islocated at the open stop position for mounting a disc or exchangingdiscs while playing another disc.

As described above, the first through the seventh operational states aresuccessively realized by rotating the crank arm 7 clockwise from thestate in which the distal end 71 a of the arm portion 71 is located atthe first rotational position S1. However, the above seven states may berealized in the reverse order by rotating the crank arm 7counterclockwise. For example, if the crank arm 7 is rotatedcounterclockwise within the angular range of ±θ from the state in whichthe distal end 71 a of the arm portion 71 is located at the seventhrotational position S7, the seventh operational state can be smoothlyshifted to the first operational state through the intermediate states.

In any of the first through the seventh operational states, the entireoperation may be stopped by the intentional turning-off of the power bythe user or due to a power failure. Even in such a case, when the poweris turned on again, it is possible to detect the rotational position ofthe crank arm 7, i.e., the state of the tray 1 and the pick-up unit 3based on the ON/OFF information of the first through the thirdmicroswitches 94-96. Therefore, the tray 1 and the pick-up unit 3 can beimmediately set to a predetermined state which may be the thirdoperational state, for example.

Specifically, for example, in the case where the power is turned off inthe second operational state and thereafter turned on again, the firstthrough the third microswitches 94, 95 and 96 are in the ON state, theOFF state and the OFF state, respectively. Based on such ON/OFFinformation, the microcomputer detects the second operational state,i.e., detects that the pick-up unit 3 is at the clamp release positionwhile the tray 1 is between the open stop position and the close stopposition. Then, to recover the third operational state from the secondoperational state, the microcomputer controls the drive motor 5 torotate the crank arm 7 clockwise. When the first through the thirdmicroswitches 94, 95 and 96 become the ON state, the OFF state and theON state, respectively, the microcomputer determines that the thirdoperational state is realized and finishes the recovery operation.

For example, in the case where the power is turned off in the sixthoperational state and thereafter turned on again, the first through thethird microswitches 94, 95 and 96 are in the OFF state, the ON state andthe OFF state, respectively. Based on such ON/OFF information, themicrocomputer detects the sixth operational state, i.e., detects thatthe pick-up unit 3 is at the clamp position while the tray 1 is betweenthe open stop position and the close stop position. Then, to recover thethird operational state from the sixth operational state, themicrocomputer controls the drive motor 5 to rotate the crank arm 7counterclockwise. When the first through the third microswitches 94, 95and 96 become the ON state, the OFF state and the ON state,respectively, as described above, the microcomputer determines that thethird operational state is realized and finishes the recovery operation.

In the foregoing embodiment, in FIG. 1, the rotational position of +θfrom the rotation reference position S0 of the crank arm 7 is set as theopen stop position for exchanging discs while not playing a disc,whereas the rotational position of −θ is set as the open stop positionfor mounting or exchanging discs while playing a disc. However, therotational position of +θ may be set as the open stop position formounting or exchanging discs while playing a disc, whereas therotational position of −θ may be set as the open stop position forexchanging discs while not playing a disc.

In the disc changer of this embodiment, even when the crank arm 7 isrotated at a constant speed to move the tray 1, the distal end 71 a ofthe arm portion 71 moves smoothly along the guide groove 100 so that thetray 1 moves while continuously changing the speed. Therefore; thesmooth movement of the tray 1 is realized. Further, since the speed ofthe movement is sufficiently reduced when the tray 1 comes close to thestop position, the shock or the operational noise upon stopping can bereduced even when a member for mechanically stopping the movement of thetray 1, such as a stopper, is provided. Also from such a point, themovement feeling can be enhanced.

As is clear from the comparison between FIGS. 11 and 30, in theconventional guide groove 1100, the boundary between the intermediatecurve 1110 and each of the left and the right straight ends 1120 and1130 is discontinuous, so that the crank arm 700 cannot be rotated tothe angle of +θ from the rotation reference position. However, in thedisc changer of this embodiment, gentle curves 120 and 130 are formed atopposite ends of the intermediate curve 110 of the guide groove 100 toeliminate such a discontinuous boundary. Therefore, the rotation rangeof the crank arm 700 can be made larger than that of the conventionaldevice.

Specifically, as shown in FIG. 11, the tray 1 can be opened to aposition at which the disc mount portion 20 of the roulette table 2 iscompletely exposed. However, as shown in FIG. 30, the conventional traycan be opened merely to a position at which the disc mount portion 20 isexposed partially, not completely. Therefore, in the disc changer of thepresent invention, the pull-out amount of the tray can be made largerthan that in the conventional device. Conversely, in the case where thetray 1 is to be pulled out from the device by the same amount, the frankarm 7 of the disc changer of the present invention can be made smallerthan that of the conventional device, which is advantageous for the sizereduction of the device.

Further, since the states of the tray 1 and the pick-up unit 3 can bedetected by the three ribs formed at the lower portion of the crank arm7 and three microswitches formed correspondingly to the ribs, thedetection can be performed easily and inexpensively.

Unlike this embodiment, it may be considered to provide totally fourmicroswitches, i.e., two microswitches for detecting the tray 1 at theopen stop position and the close stop position and two microswitches fordetecting the pick-up unit 3 at the clamp position and non-clampingposition. In this embodiment, however, the detection can be performed byusing only three microswitches 94-96, so that the number of switches canbe minimized.

In the foregoing embodiment, the length of the arm portion 71 and theguide groove 100 can be determined based on the amount of movement ofthe tray 1 and the angular range in which the crank arm 7 rotates andcan be varied appropriately in accordance with the specification.Further, as to the ON/OFF states of the first through the thirdmicroswitches 94-96, it is only necessary that the respective ON/OFFstates in the first through the seventh operational states differ fromeach other. Based on such ON/OFF states, the positional relationshipbetween the first through the third microswitches 94-96 and the firstthrough the third ribs 74-76 can be determined. Further, although thecylindrical cam 8 is used in the above embodiment, a plate cam may beused instead of the cylindrical cam 8.

1. A disc changer comprising: a tray for carrying a plurality of discsmounted thereto, the tray being arranged in a housing movably back andforth into and out of the housing; a reproducer arranged at apredetermined position in the housing to be displaceable up and down forreproducing information recorded on a disc while clamping the disc onthe tray; a driving source for generating a driving force for performingthe in-out movement of the tray and the displacement of the reproducer;and a driving force transmission for transmitting the driving forcegenerated at the driving source to the tray and to the reproducer whileswitching between the tray and the reproducer, the transmissioncomprising a guide groove formed at a lower surface of the tray toextend right and left, a cam for displacing the reproducer up and downto shift the reproducer between a disc clamp position and a clamprelease position, and a crank arm arranged below the tray in thehousing, the crank arm including a disc-like rotation portion which isrotatable by the driving force of the driving source, an arm portionprojecting radially outward from an outer circumference of the rotationportion and having a distal end slidably engaging the guide groove, anda connection portion formed at part of the outer circumference of therotation portion for connection to the cam to transmit a rotationalforce of the rotation portion to the cam when the distal end of the armportion moves through an intermediate portion of the guide groove;wherein the guide groove has a bow shape comprising an arcuateintermediate curve generally conforming to an arcuate path along whichthe distal end of the arm portion moves due to the rotation of the crankarm, and left and right end curves extending from opposite ends of theintermediate curve and curved opposite to the intermediate curve;wherein the cam is cylindrical and has a circumferential surface part ofwhich is formed with a cam groove inclined with respect to a verticaldirection and another part of which is formed with teeth; and whereinthe connection portion of the crank arm comprises teeth formed at acircumferential surface of the rotation portion at a position whichfaces the teeth of the cylindrical cam to mesh with the teeth duringwhen the distal end of the arm portion moves through the intermediatecurve of the guide groove.
 2. The disc changer according to claim 1,wherein the rotational force of the crank arm is transmitted to the trayduring when the distal end of the arm portion moves through the left endcurve or the right end curve of the guide groove, whereas the rotationalforce of the crank arm is transmitted to the reproducer via the camduring when the distal end of the arm portion moves through theintermediate curve of the guide groove.
 3. The disc changer according toclaim 2, wherein the tray pulled out of the housing can be kept at anopen stop position when the distal end of the arm portion of the crankarm in a process of moving from the left end curve or right end curvetoward the intermediate curve of the guide groove reaches apredetermined position in the left end curve or the right end curve. 4.The disc changer according to claim 3, wherein the predeterminedposition is adjacent a boundary between the right end curve or the leftend curve and the intermediate curve of the guide groove.
 5. The discchanger according to claim 1, wherein a detector for detectingoperational states of the tray and the reproducer is provided under therotation portion of the crank arm.
 6. The disc changer according toclaim 5, wherein the detector detects the operational states of the trayand the reproducer by detecting a position of the distal end of the armportion of the crank arm in the guide groove.
 7. The disc changeraccording to claim 6, wherein the detector detects that the distal endof the arm portion of the crank arm is positioned in the intermediatecurve of the guide groove, in the left end curve of the guide groove, inthe right end curve of the guide groove, at the position in the left endcurve of the guide groove which corresponds to the open stop position ofthe tray, and at the position in the right end curve of the guide groovewhich corresponds to the open stop position of the tray.
 8. The discchanger according to claim 6, wherein the detector comprises a pluralityof ribs respectively formed on a plurality of concentric tracks on alower surface of the rotation portion of the crank arm, a plurality ofswitches provided below the rotation portion of the crank arm atpositions which face the respective tracks, and a determiner fordetermining the position of the distal end of the arm portion of thecrank arm in the guide groove based on information as to switchingoperation of the switches performed by the ribs in accordance with therotation of the rotation portion of the crank arm.
 9. The disc changeraccording to claim 8, wherein each of the ribs has opposite ends each ofwhich is formed with a downward slope.
 10. The disc changer according toclaim 8, wherein the determiner determines the position of the distalend of the arm portion of the crank arm in the guide groove based oncombination of ON/OFF information of the plurality of switches.
 11. Adisc changer comprising: a tray for carrying a plurality of discsmounted thereto, the tray being arranged in a housing movably back andforth into and out of the housing; a reproducer arranged at apredetermined position in the housing to be displaceable up and down forreproducing information recorded on a disc while clamping the disc onthe tray; a driving source for generating a driving force for performingthe in-out movement of the tray and the displacement of the reproducer;and a driving force transmission for transmitting the driving forcegenerated at the driving source to the tray and to the reproducer whileswitching between the tray and the reproducer, the transmissioncomprising a guide groove formed at a lower surface of the tray toextend right and left, a cam for displacing the reproducer up and downto shift the reproducer between a disc clamp position and a clamprelease position, and a crank arm arranged below the tray in thehousing, the crank arm including a disc-like rotation portion which isrotatable by the driving force of the driving source, an arm portionprojecting radially outward from an outer circumference of the rotationportion and having a distal end slidably engaging the guide groove, anda connection portion which is formed at part of the outer circumferenceof the rotation portion for connection to the cam to transmit arotational force of the rotation portion to the cam when the distal endof the arm portion moves through an intermediate portion of the guidegroove; wherein a detector is provided under the rotation portion of thecrank arm for detecting, at least, a state in which the tray is pulledout from the housing, a state in which the tray is accommodated in thehousing, a state in which the reproducer clamps a disc, and a state inwhich the reproducer releases a disc.
 12. The disc changer according toclaim 11, wherein the detector comprises a plurality of ribsrespectively formed on a plurality concentric tracks on a lower surfaceof the rotation portion of the crank arm, a plurality of switchesprovided under the rotation portion of the crank arm at positions whichface the respective tracks, and a determiner for determining theoperational state of the tray and the reproducer based on information asto switching operation of the switches performed by the ribs inaccordance with the rotation of the rotation portion of the crank arm.13. The disc changer according to claim 12, wherein each of the ribs hasopposite ends each of which is formed with a downward slope.
 14. Thedisc changer according to claim 12, wherein the determiner determinesthe operational state of the tray and the reproducer based oncombination of ON/OFF information of the plurality of switches.
 15. Thedisc changer according to claim 11, wherein the detector comprises threeribs respectively formed on a plurality concentric tracks on a lowersurface of the rotation portion of the crank arm, thee switches providedunder the rotation portion of the crank arm at positions which face therespective tracks, and a determiner for determining the operationalstates of the tray and the reproducer based on information as toswitching operation of the switches performed by the ribs in accordancewith the rotation of the rotation portion of the crank arm, saidoperational states including a state in which the tray is pulled outfrom the housing with the reproducer not clamping a disc, a state inwhich the tray is moving with the reproducer not clamping a disc, astate in which the tray is accommodated in the housing with thereproducer not clamping a disc, a state in which the tray isaccommodated in the housing with the reproducer moving up or down, astate in which the tray is accommodated in the housing with thereproducer clamping a disc, a state in which the tray is moving with thereproducer clamping a disc, and a state in which the tray is pulled outof the housing with the reproducer clamping a disc.
 16. A disc changercomprising: a tray for carrying a plurality of discs mounted thereto,the tray being arranged in a housing movably back and forth into and outof the housing; a reproducer arranged at a predetermined position in thehousing to be displaceable up and down for reproducing informationrecorded on a disc while clamping the disc on the tray; a driving sourcefor generating a driving force for performing the in-out movement of thetray and the displacement of the reproducer; and a driving forcetransmission for transmitting the driving force generated at the drivingsource to the tray and to the reproducer while switching between thetray and the reproducer, the transmission comprising a guide grooveformed at a lower surface of the tray to extend right and left, a camfor displacing the reproducer up and down to shift the reproducerbetween a disc clamp position and a clamp release position, and a crankarm arranged below the tray in the housing, the crank arm including adisc-like rotation portion which is rotatable by the driving force ofthe driving source, an arm portion projecting radially outward from anouter circumference of the rotation portion and having a distal endslidably engaging the guide groove, and a connection portion formed atpart of the outer circumference of the rotation portion for connectionto the cam to transmit a rotational force of the rotation portion to thecam when the distal end of the arm portion moves through an intermediateportion of the guide groove; wherein the guide groove has a bow shapecomprising an arcuate intermediate curve generally conforming to anarcuate path along which the distal end of the arm portion moves due tothe rotation of the crank arm, and left and right end curves extendingfrom opposite ends of the intermediate curve and curved opposite to theintermediate curve; and wherein a detector for detecting operationalstates of the tray and the reproducer is provided under the rotationportion of the crank arm.